The present disclosure relates to harvesting articulated (jointed) combines and more particularly to improved airflow in the forward tractor or crop processing power unit (PPU) (U.S. Ser. No. 15/642,799; U.S. Publication 2018/0007830) having dual engines (U.S. Ser. No. 15/643,685; U.S. Publication 2018/0009305) with all grain stored in a rear grain cart and that permits additional sieve capacity concomitant with tailings return thereto (U.S. Pat. No. 10,045,488).
U.S. Ser. No. 15/642,799 and U.S. Ser. No. 15/649,684 in tandem describe an airflow system involving many components of the harvester that require fan driven airflow through various components of the power system and the separation systems of the machine. Since the movement of the total air system, as it interacts with the separation systems of the machine, is powered by fans that are not physically close to one another, the issue of driving the (4) separate fans is difficult when done by belt or similar drive mechanism. Compound that with the notion that it would be beneficial, if not essential, to the separation process to have all the fans change their speed in unison should the operator or an electronic control system choose to change the speed of the main cleaning fan.
The four fans described in the related patent applications are (a) the main cleaning fan assembly, (b) the charge fan assembly, and (c) a right side tailings fan assembly, and (d) a left side tailings fan assembly. The charge fan assembly sits high up near the top of the chassis, above and behind the operator's cab, and receives air from a cooling fan assembly via the hydraulic cooling radiator. The cleaning fan assembly sits well below the cab and under the feeder mechanism, accepting the air from the charge fan, and accelerating and directing it rearward under and through the cleaning sieves. The two tailings fan assemblies are located on the outward regions of the front chassis, in the protrusion of the chassis that juts outward rear of the front tires, and are used to pull in addition ambient air for blowing up, through, and under the tailings sieves, one on each side of the machine. By illustration, it is seen that driving all these fans is a difficult task, and coordination of the speeds of these fans could be a difficult, complicated, and expensive proposition at best. These tailings assemblies may be referred to herein as bonus assemblies.
However, if one chooses to drive each of these fans by a hydraulic motor, an interesting and opportune arrangement presents itself. All of these motors can be driven on a single series hydraulic circuit, such that the same volume of oil can run through the large, fast cleaning fan, assembly, then to the smaller yet faster charge fan assembly, and then down to the two tailings fan assemblies. Such a hydraulic circuit is possible if the flow can be equally and efficiently separated into two identical volumes of flow when leaving the charge fan assembly. In this manner, a change in the amount of hydraulic flow to the cleaning fan assembly to change its speed and air output volume will necessarily change the speed and subsequent air flow volumes of each of the other fans. Since each of these fan assemblies are in some manner affecting the velocity of air flowing through the separation process that by definition must vary with the related changes of density and air drag of different types of grains being cleaned in the system.